This invention relates to lead-acid batteries, particularly to valve-regulated lead-acid batteries including catalysts which aid in the recombination of hydrogen with oxygen within the battery.
Certain catalysts are known to aid in the recombination of hydrogen with oxygen within a lead-acid battery environment. These catalysts, which are generally noble metals, with palladium being preferred, serve to xe2x80x9cmop upxe2x80x9d the hydrogen and to recombine hydrogen released in the course of battery operation with oxygen to make water.
This recombination serves to counteract loss of water during battery operation. Loss of water would otherwise occur if the hydrogen were left to remain in a free state. This is because free hydrogen can actually diffuse through the case of the battery and escape to atmosphere. Loss of hydrogen is a function of relative partial pressure of hydrogen inside and outside of the battery case. The small size of hydrogen molecules permits them to diffuse through nearly any non-metallic material, including the plastics widely used to fabricate lead-acid battery cases. Hence, if free hydrogen is not captured and recombined with oxygen, the net result is loss of water by the battery with the battery eventually drying out and failing.
Typically, catalyst material is provided in the form of pellets in order to maximize the surface area of the catalyst available for effectuating the catalytically recombining reaction of hydrogen with oxygen within the battery.
In one of its aspects, this invention provides a recombinant lead-acid battery having a case, a plurality of lead-acid cells within the case, where each cell includes a plurality of positive and negative lead metal plates, and absorbent separator material between at least some of the positive and negative plates. The case may include partitions for separating adjacent cells one from another with portions of the partitions being spaced from the case to define space for vapor migration among cells. The battery preferably further includes a catalyst unit removably connected to the case and communicating with the vapor migration space for enhancing recombination of hydrogen and oxygen in the water at least partially in vapor phase within the battery. The catalyst unit is preferably at least partially within the case. The catalyst is preferably palladium.
In another of its aspects, this invention provides a recombinant lead-acid battery including a case, a plurality of lead-acid cells within the case, where each cell comprises positive and negative Lead metal plates, and absorbent separator material between at least some of the positive and negative plates. The cells are preferably in vapor communication one with another. The battery further preferably includes a plurality of optionally removable catalyst units in vapor communication with the cells for enhancing recombination of hydrogen and oxygen into water at least partially in vapor phase within the battery where the plurality of catalyst units is preferably no greater than the number of lead-acid cells. At least some of the catalyst units are preferably at least partially within the battery case. Some of the catalyst units may be completely within the battery case.
The catalyst is preferably palladium.
In yet another of its aspects, this invention embraces a method for operating a recombinant lead-acid battery having a case, a plurality of lead-acid cells within the case, with each cell including positive and negative lead metal plates, and absorbent separator material between at least some of the positive and negative plates, where the method includes placing the cells in vapor communication one with another and placing a plurality of discrete catalyst units no greater than the number of cells in vapor communication with the cells, to enhance recombination of hydrogen and oxygen in the vapor phase water within the battery.
In yet another of its aspects, this invention provides a recombinant lead-acid battery including a case having at least one venting aperture therein, a plurality of positive and negative lead metal plates within the case and absorbent separator material between at least some of the positive and negative plates. The battery further includes a vent valve assembly within the aperture including valve means for relieving pressure internal of the battery in excess of a predetermined level above ambient, a catalyst cage extending into the case from the assembly within the aperture and catalyst material retained within the cage and in vapor communication with the plates for enhancing recombination of oxygen and hydrogen involved in the plates in the water within the battery.
In still another of its aspects, this invention provides a recombinant lead-acid battery including a case having at least one venting aperture therein, a plurality of lead-acid cells within the case with each cell including positive and negative lead metal plates and absorbent separator material between at least some of the positive and negative plates. At least some of the cells are preferably in vapor communication one with another. In this aspect of the invention, the battery further yet preferably includes a vent valve assembly within the aperture which is in vapor communication with the vapor communicating cells and includes a valve member for relieving pressure internal of the vapor communicating cells in excess of a predetermined level above ambient, a catalyst cage extending into the case from the valve assembly within the aperture and catalyst material retained within the cage and being in vapor communication with the communicating cells for enhancing recombination of hydrogen and oxygen evolved at the plates of the cells into water within the battery.
In yet another of its aspects this invention embraces a method for operating a recombinant lead-acid battery having a case, a plurality of lead-acid cells within the case with each cell including positive and negative lead metal plates and absorbent separator material between at least some of the positive and negative plates, comprising placing the cells in vapor communication one with another and placing a plurality of discrete catalyst units forming portions of vent valve assemblies into venting apertures in said case so that discrete catalyst unit portions of said vent valve assemblies are in vapor communication with said cells thereby enhancing recombination of hydrogen and oxygen into vapor phase water within the battery.
This invention in another one of its aspects provides a vent plug-catalyst carrier assembly for a lead-acid battery. The vent plug-catalyst carrier assembly may preferably be provided as an original equipment part of a lead-acid battery or may be easily retrofitted into lead-acid batteries already in commercial service, provided the battery case has structure for receiving and fixing in place a new vent structure.
In the apparatus aspect of the invention, a cage for the catalyst is preferably permanently affixed to the battery vent plug with the cage preferably permanently retaining a catalyst cartridge in a floating disposition within the cage. The cage is preferably disposed at the leading edge of a narrow neck structure extending into the vent hole. Floating disposition of the catalyst in the cage minimizes risk of cage fracture and catalyst destruction as the battery case expands and contracts due to pressure build-up within the battery, temperature changes, plate growth and the like.
The invention relates further to a vent valve-catalyst carrier combination structure for and in combination with a lead-acid battery. The vent valve preferably has a hollow tubular housing at least part of which preferably fits within a vent passage into the battery casing. Other parts of the tubular housing adjoin the casing such that a sealing member may be placed between the casing and vent valve. A barrier preferably extends across the housing for blocking passage of gases. The valve opening extends through the barrier and is normally covered by a flexible valve member. The valve member is preferably supported in normally closed position but arranged to yield to battery internal pressure of a predetermined level over atmospheric.